Caching in: Western Digital sheds light on new hybrid technology for mobile drives

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Western Digital and SanDisk jointly announced a new partnership earlier this week. The two companies are going to work together to develop their own brand of solid state hybrid drive (SSHD), claiming that the combined WD Black will debut in 5mm, 7mm, and 9.5mm form factors, offer 500GB of storage, and compete against Seagate’s own hybrid drives like the Laptop Thin lineup. Unlike Seagate, which is on its third iteration of hybrid technology, Western Digital is coming at this fresh — and it’s not using the same cache approach as its competitor.

To date, we’ve seen two general methods of data caching come to market. First, there’s the approach Seagate takes with the Momentus XT/Laptop Thin series. The entire cache process happens below the OS level; there are no drivers, no configuration details, no visible sign that any data is being cached at all. Up until recently, Seagate didn’t cache writes, which limited the potential for data loss. The Laptop Thin series introduced some support for write-caching (in which data is reported as having been written to the drive before the actual write is finished). To ensure that data wasn’t lost, Seagate added capacitors to the final product. In the event of an unexpected power loss, the Laptop Thin series stores enough power to finish writing data before powering down. Since we’re talking about NAND, that doesn’t take long.

The other method of caching uses software like Smart Response Technology or Nvelo’s Dataplex. Nvelo has been acquired by Samsung since we wrote our review, but the approach hasn’t changed. Both Intel and Nvelo install an extremely low-level driver that monitors file system activity and decides which data should be cached on the SSD to ensure maximum performance. Both drives are hooked to the system south bridge, which handles the synchronization. Data loss is possible in these scenarios, though we never encountered a problem with RST or Dataplex, and both companies stressed that they take steps to minimize the chance of data being lost.

So, how does WD cache its data? With a mixture of both approaches. As Tech Report explains, WD has gone for the driver-level approach for file management, but the NAND flash and magnetic media don’t communicate over the main system SATA bus; they’re directly linked by an internal SATA bridge chip. Both reads and writes will be cached, but Western Digital could theoretically incorporate a capacitor approach like Seagate’s to ensure that write data is saved in the event of a power loss.

Western Digital is incorporating 8-24GB of NAND in its drives (Seagate offers a static 8GB of flash) and has heavily customized the firmware. PC manufacturers will apparently have the option of choosing between Western Digital’s own driver or an Intel driver, with TR reporting that the WD driver was built in-house and is capable of using system memory as part of the caching scheme. Presumably the WD driver also supports AMD systems; the Intel driver would obviously be limited to Intel’s own chipsets.

For now, this is a mobile-only game, but it’s easy to see where the road will lead if these hybrid products take off. The VelociRaptor family is an easy target for this type of integration, and as we tested back in August, combining the VR with a cache solution did improve overall performance in some tests. This is the logical next step for the cache drive approach. Integrating both drives into a single package allows the same performance profile in an ultrabook where multiple drive bays aren’t an option. Western Digital isn’t shipping samples quite yet, but we’ll have performance figures as soon as they’re available.

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chojin999

“PC manufacturers will apparently have the option of choosing between Western Digital’s own driver or an Intel driver”–Seriously ? These WD hybrid drives need OS drivers to use the SSD caching ? That means that the DSP controller onboard it’s really cheap and can’t manage everything in a transparent manner.
The Seagate Hybrid HDU+SSD SSHD drives don’t need any OS nor UEFI BIOS driver to use the onboard SSD. Everything it’s transparent to OS,BIOS and user.
Until WD switches to a proper transparent design revising this mess I surely avoid buying any of these SSHD drives.

Guest

Have you EVER written a comment that was useful in any way?? Most people who are completely uneducated on a subject would refrain from commenting, but it’s like you’re on a personal crusade to see how many downvotes you can get… Here’s a tip: When you have no idea what you are talking about, just step away from the keyboard. Nobody wants to read your moronic comments, and it would just take way to long to go into detail about why your comment is stupid. Not to mention you wouldn’t listen anyway, because in your own warped and twisted fantasy world you are right and everyone else is wrong and should listen to you…

chojin999

You are the one here that has no clue what he is talking about, really.

Maybe you are a Western Digital employee and you don’t like my comment because I stated an obvious product flaw.

dns7950

I’m just going to break down your comment into smaller pieces, and
then make fun of it, if you don’t mind.. This is comedic gold!

“You are the one here that has no clue what he is talking about, really.”

HAHA! You took my words, and said the same thing about me! Very original, great comeback!

“Maybe you are a Western Digital employee and you don’t like my comment because I stated an obvious product flaw.”

Suggesting I must be working for WD because I don’t think you should bash their unreleased product that you have never used. That’s very clever, nobody on the internet has ever thought of that witty response before.

“You are afraid of people understanding that the Seagate hybrid drives are a better design,uh?”

So by your logic (if you can call it that), I guess you must work for Seagate,uh?

“Then Western Digital should have put more effort into delivering a proper product instead of a lazy design.”

The product hasn’t been released yet, so you can’t really say it’s an improper pruduct (well, obviously you can, but it makes you look kinda stupid..) Something tells me you couldn’t do any better..

“Requiring OS drivers to use the SSD on a SSHD drive it’s just plain dumb and it surely clearly means that the actual performance is lower too.”

As it states in the article, SSHD stands for “solid state hard drive”, so you are actually calling it a “solid state hard drive drive”. That is surely clearly redundant, repetitive and unecessary (really, absolutely,positively!). Saying that requiring drivers must mean lower performance shows a complete lack of understanding of computers. Maybe you should increase the performance of your PC by uninstalling all your drivers for any hardware you have? Let me know how that works out for you.

chojin999

The immature little kid here it’s you. And you are obviously an ignorant too.

You keep babbling nonsense with no knowledge of what you are talking about and you go on attacking me personally like you were in kindergarten.

Or do you think that software based RAID systems and/or pseudo-DSP RAID controllers that rely on CPU to work and just offload a small percentage of the calculations are better than expensive Enterprise class full hardware DSP controllers, uh ?

Here it’s just the same concept.

If you had any knowledge of the matter you wouldn’t have started attacking me telling nonsense in a childish way.

However, you might still be a WesternDigital employee that decided to act childish like that as a cover up.

Only other option you are a little kid or an adult acting childish, still completely ignorant and absolutely arrogant.

Guest

What you’ve just said is one of the most insanely idiotic things I have ever heard. At no point in your rambling, incoherent response were you even close to anything that could be considered a rational thought. Everyone in this room is now dumber for having listened to it. I award you no points, and may God have mercy on your soul.

[sigh...] I give up. I’m not even going to start pointing out everything wrong with your comment because I’d be here forever.

chojin999

You are so childish and ignorant. No matter how many fake accounts you use to vote you up and insult me.

You clearly have no clue what you are talking about.

dns7950

I only have 1 account. Making fake accounts to vote my own comments up would be a complete waste of time, since I actually don’t care what people on the internet think.. There are millions of morons who would argue that “artists” such as Justin Bieber, Ke$ha, Nicki Minaj, Lil Wayne, and Skrillex are better than musicians like Led Zeppelin, The Beatles, The Rolling Stones, Pink Floyd and Metallica. That doesn’t change the fact that my @$$ has more musical talent than most of them, since the last time I ate chili I passed gas that was more musical, and stunk less than almost every song in the top 40. I’m very well aware of the fact that there are millions of retarded people on the internet, and many people disagree with me and may vote down my comments. I honestly couldn’t care less though, since most people with a functioning brain would agree with me…

P.S. It is said that people often accuse others of what they themselves are guilty of, so maybe that could explain why your comments actually have a couple upvotes…

chojin999

You think to be smart uh ?

You should watch your steps then because just here it seems you used two different accounts to log-in and reply to me “Guest” user…
So now you are revealing that you got the “dns7950″ account too…
How many accounts you are actually using it’s obviously unknown.
And you go on accusing me of using multiple accounts. Pathetic.

dns7950

“You think to be smart uh ?”

Do you even grammar?

“You should watch your steps then because just here it seems you used two different accounts to log-in and reply to me “Guest” user…
So now you are revealing that you got the “dns7950″ account too…
How many accounts you are actually using it’s obviously unknown.
And you go on accusing me of using multiple accounts. Pathetic.”

You, sir, are a moron. Like a stated in the previous comment, I have only one account. “Guest” is not an account. If you wish to comment anonymously, you can choose to delete your comment. The comment remains, but your name is removed, and becomes “Guest”. So, yes, dns7950 is the “Guest” above, but as I have already said, I ONLY HAVE ONE ACCOUNT. You would make a lousy detective, and I certainly hope you never get jury duty…

chojin999

You can post as “Guest” with whatever account. No one can check that other than Disqus itself.

You can have dozens of accounts.

And why posting as “Guest” first and then revealing your account all of a sudden ?

Keep insulting me.. you prove to be so smart and cool and mature.. a genius..

dns7950

“You can post as “Guest” with whatever account. No one can check that other than Disqus itself.”

Yeah, that’s pretty much what I just told you in my last comment. Congratulations, you actually can comprehend SOME of what you read. I never knew you had it in you..

“You can have dozens of accounts.”

Yeah, but that sounds very tedious. I only waste time when it is somehow amusing or entertaining, and that just sounds boring…

“And why posting as “Guest” first and then revealing your account all of a sudden ?”

Because why not? I usually only comment when it’s completely relevant to the article, so I didn’t want to tarnish my username by making fun of idiots. But then somewhere along the line your stupidity became so overwhelming that I realized that no intelligent person is going to care what you think, and I might as well take credit for my own comments.

“Keep insulting me.. you prove to be so smart and cool and mature.. a genius..”

Thanks for the advice, I will definitely keep insulting you if you continue to make ridiculous, uneducated comments on the articles here.

chojin999

Go on keep showing the world what an arrogant childish guy you are…

Phobos

MG, this is too much LOLLOL. So I’m guessing chojin works for intel, seagate and IBM.
Oh yes I forgot where are the cheap AMD APU’s?

Bwheetley

The Seagate Momentus Hybrid 750GB drive does not work the way it is advertised in all systems, so perhaps it needs it’s own drivers as well. I have one in my MacBook Pro. While it does store my data, it never, ever spins down and drains my battery in about 1 1/2 hours. If you search the internet for that drive and MacBook Pro, you will see many people are having problems with them. I came across this article while searching for a different drive that I can place in my MacBook.

Does anybody know if any of the upcoming WD SSHDs (either the 5mm, 7mm, and/or the 9.5mm ones) will be any larger than a measley 500 GB?

Because, hopefully, WD will use 7200 RPM drives, but if their only size is 500 GB, AND it runs at 5400 RPM, that is not worth the mediocre speed boost you’ll get over, say the 750 GB Seagate one, or even the 1 TB HGST mechanical HD (in my opinion)…

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